Comm2 Day 4: Happy Birthday Alfio!

As you can see in the above picture, we have a new minimum-force basis set to try (thanks Fernando!). As soon as we get everything lined up, we’ll test it on the CRO.

Speaking of the CRO, yesterday was crazy. So crazy that none of us had much energy left (at 1am) to write a long ‘splainy blog post. So here’s a little more about what was going on. The CRO is a tiny mirror inside a cup, which has a pinhole on the top. The CRO is suspended at the focus of the ASM, and we send light from an artifical star inside the W-unit up to the secondary, which focuses it into the pinhole, and the CRO reflects it back to the secondary exactly as it came in. CRO stands for Calibration Return Optic (note: it is NOT a retro-reflector! (right Alan?)), both C-R-O and Crow are considered correct pronunciations.

The CRO pinhole is very small, so we have to have it exactly on the optical axis of the telescope. To align it, we use two crosses, one at the W-unit itself, and one on the back of the CRO. The real magic, thanks to Armando and company, is to use a digital camera with a wide focus range to first focus on the W-unit cross, then on the CRO cross, and move the camera until the two crosses line up. From there we move the CRO itself until the reflection from the CRO is lined up with the crosses.

So, step 1 is: Make crosses. In Katie’s post yesterday you saw how the cross was made on the back of the CRO. We also had to re-make the cross on the W-unit. Armando made one using some wire and a rubber band to keep it tight, but the rubber band disintegrated over the last few months. For some reason, it fell to me to attempt to re-create some fine Italian craftsmanship:

We replaced the rubber band with Katie’s hair tie.

Step 2 is: Line up the CRO secondary and instrument axis using the cross at the instrument and the mark on the bottom of the CRO.

Alfio and Marco set up Laird’s camera on Vanessa’s tripod to check the alignment of the CRO.

Step 3 is: move the CRO (this time by moving the secondary vane-ends) so that the reflection of the measuring camera itself. off the secondary, is centered on the crosses.

The final result: The new fiducial cross of tape on the CRO (thick orange X in focus in center) is lined up with the cross of string on the W-unit plate (out of focus) lined up with the dark rectangle which is the axis of Laird’s camera.

Step 4: blog it
Done.

Alfio, Marco, and Katie depart the Clay telescope, heading down for lunch.

Today we finished the Clio cool-down, and after lunch moved Clio from the Aux and mounted it (her?) on the telescope.

After re-seating a vacuum hose, we got Clio down to 55KKatie, Vanessa, and Victor unhooking Clio from its resting place in the Aux.Vanessa admires her handiwork. Clio is back on the telescope, ready to go.

After Clio was on, the grad students kept working.

This is what life’s like when you’re a NASA Sagan Fellow. Or so I’m told.

After dinner, we proceeded with aligning the system for CRO tests.

An almost round (opinions vary) pupil using our alignment laser. This is light reflected off the secondary, into the CRO, and back off the secondary.

A herd of burros came to the watering hole close to the lodge today.

A baby burro.The south end of a north bound burro.

We missed sunset tonight, but we never miss a Vizzy photo-op.

A perfect Vizcacha profile.A moon shot by Vanessa.

Quotes:
Laird: “If we don’t get good suckage, it’s not going to work.”

Laird: “It’s like yoga”
Povilas: “It’s like hot yoga!”

Laird: “I often get a little confused about what’s hot and what’s not.”

Vanessa: “I only took 4 pictures today. I wasn’t very productive” (the blog is our #1 priority)